The invention is related to the field of forming flexible abrasive members. Such members, which may take the form of circular pads for grinding discs, or of loop shaped bands, are generally manufactured by depositing metal on a substrate, in the presence of abrasive particles. These abrasive particles become embedded in the metal deposits, and provide the abrasive action of the abrasive member.
The metal deposits, which support the abrasive particles, are usually adhered to a substrate in order to provide a strong bond. This bond should be strong enough to withstand the high wear and tear which occurs during grinding.
From the state of the art, several methods are known for manufacturing such abrasive members. According to GB-A-1375571, a sheet is embedded in a backing material, leaving only isolated areas exposed on one side of the sheet. Subsequently, a metal together with embedded abrasive particles is deposited on these isolated areas by means of a plating process.
This prior art method has the disadvantage that, due to the fact that the isolated areas are only on one side of the sheet, the process of depositing the metal is rather slow. The isolated areas should be activated by a metal activation bath, then be cleaned in a separate cleaning bath and be plated by electroplating. Apart from the slow progress of this method, it is environmentally unfriendly having regard to the chemicals used in the activating and cleaning baths. Furthermore, the quality of the adhesion between metal deposits and the sheet is relatively poor.
GB-A-1534448 teaches a method for manufacturing an abrasive member by masking off a backing sheet with a mask such as a perforated tape, plastic, paint, photoresist rubber or the like, and by subsequently depositing a metal with abrasive particles on isolated exposed portions of the backing sheet.
Also from EP-B-263785 a method of this kind is known. Both prior art methods suffer from the problem that the metal deposits cannot be formed within a well defined boundary, in case the mask is applied on one side of a porous substrate. In those cases, the non covered side of the substrate will be plated together with the isolated, exposed areas on the other side. This results in a long production time, and also in a less flexible product.
The object of the invention is to provide a method for manufacturing a precision flexible abrasive member which is both cheap and quick, and which provides a better adherence of the metal deposits onto the substrate. This object is achieved by a method of manufacturing a flexible abrasive member, comprising the steps of:
providing a porous substrate,
impregnating the substrate with an electrically isolating material,
treating a side of the impregnated substrate so as to provide areas with different properties as to water or solvent resistance,
washing the impregnated substrate with water or a solvent so as to wash away the areas with a relatively low water or solvent resistance for obtaining a prepared substrate with discrete areas,
placing the prepared substrate in a metal deposition bath, and
depositing metal in said discrete areas in the presence of abrasive particles so as to form abrasive metal deposits.
By impregnating the substrate, it is fully and reliably covered on both sides. This means that only in discrete areas from which subsequently the impregnating material is removed, the porous substrate is accessible. The rest of the substrate is fully inaccessible, which ensures that metal deposition only takes place in very well defined, discrete areas.
As before, it is still possible to create open, discrete areas only on one side of the substrate. However, for obtaining a good adherence, it is preferred to create open areas on both sides of the substrate. In case the discrete areas thus obtained on both sides of the substrate are congruent, the substrate is embedded fully in the metal deposits, thus providing a strong bond.
Alternatively, it is possible to treat the other side of the substrate fully. In that case, said side is completely covered by the electrically isolating material.
The treatment referred to before, by means of which discrete areas are obtained, can take several forms. Preferably, said treatment comprises the steps of:
impregnating the substrate with a resin, and
exposing the discrete areas to UV-light so as to render them water or solvent resistant for forming a prepared substrate.
The discrete areas may be defined by the openings of a film placed between a source of UV-light and the side in question of the substrate.
The step of impregnating the substrate may be carried out in several ways as well. According to a first possibility, the substrate is impregnated by dip coating. Separate pieces of substrate material are dipped in a container comprising a fluid coating material. After removing and drying the coating, the substrate can be processed further. This method is in particular suitable for small batches.